Re: [Qemu-devel] [PATCH 30/52] target-m68k: add scc/dbcc

[Richard Henderson]

On 05/04/2016 10:12 AM, Laurent Vivier wrote:
> Signed-off-by: Laurent Vivier <address@hidden>
> ---
>  target-m68k/translate.c | 46 ++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 46 insertions(+)
>
> diff --git a/target-m68k/translate.c b/target-m68k/translate.c
> index 5914185..cd656fe 100644
> --- a/target-m68k/translate.c
> +++ b/target-m68k/translate.c
> @@ -1096,6 +1096,49 @@ static void gen_jmp_tb(DisasContext *s, int n, uint32_t 
> dest)
>      s->is_jmp = DISAS_TB_JUMP;
>  }
>
> +DISAS_INSN(scc_mem)
> +{
> +    TCGLabel *l1;
> +    int cond;
> +    TCGv dest;
> +
> +    l1 = gen_new_label();
> +    cond = (insn >> 8) & 0xf;
> +    dest = tcg_temp_local_new();
> +    tcg_gen_movi_i32(dest, 0);
> +    gen_jmpcc(s, cond ^ 1, l1);
> +    tcg_gen_movi_i32(dest, 0xff);
> +    gen_set_label(l1);

Use setcond + neg to avoid the jump.  Since you are storing a single byte, it 
doesn't matter that the neg produces -1 instead of 0xff.

> +    DEST_EA(env, insn, OS_BYTE, dest, NULL);
> +    tcg_temp_free(dest);
> +}
> +
> +DISAS_INSN(dbcc)
> +{
> +    TCGLabel *l1;
> +    TCGv reg;
> +    TCGv tmp;
> +    int16_t offset;
> +    uint32_t base;
> +
> +    reg = DREG(insn, 0);
> +    base = s->pc;
> +    offset = (int16_t)read_im16(env, s);
> +    l1 = gen_new_label();
> +    gen_jmpcc(s, (insn >> 8) & 0xf, l1);
> +
> +    tmp = tcg_temp_new();
> +    tcg_gen_ext16s_i32(tmp, reg);
> +    tcg_gen_addi_i32(tmp, tmp, -1);
> +    gen_partset_reg(OS_WORD, reg, tmp);
> +    tcg_gen_brcondi_i32(TCG_COND_EQ, tmp, -1, l1);
> +    update_cc_op(s);
> +    gen_jmp_tb(s, 1, base + offset);
> +    gen_set_label(l1);
> +    update_cc_op(s);
> +    gen_jmp_tb(s, 0, s->pc);

Pull the update_cc_op up to the top, so as to only generate one copy.


r~